Impacts of low-head, run-of-the-river dams on migratory fish movements depend on the structure of the dam, river hydrology, and the ability of fish to navigate the tailrace environment. Here, we present results from a 3-year movement study in which telemetered Paddlefish Polyodon spathula and Smallmouth Buffalo Ictiobus bubalus were tracked as they approached and sometimes migrated past Claiborne Lock and Dam (CLD), a low-use low-head lock-and-dam structure on the Alabama River. A spillway portion of the dam is periodically inundated during early spring, dependent on precipitation and releases from the next upstream dam. Our goals were to (1) quantify dam passage rates for both species, (2) assess the importance of factors affecting passage success, and (3) quantify space use patterns in the tailrace. Both species exhibited annual upstream migrations during the study period. Correlation of daily average river position versus the CLD hydrograph showed that movements by both species appeared to be related to flow variation. Passage efficiency (range = 10.7-30.2%) varied between species and among years, with tailrace gauge height being the most important factor affecting passage success for both species. Using an acoustic positioning system in the tailrace, we quantified space use by individuals of both species. Time spent in the tailrace (mean = 3.9 continuous days; range = 0-94 continuous days) did not differ between individuals that passed and those that did not pass. Fine-scale position estimates showed that space use differed between species, across gauge heights, and between individuals that passed and those that did not pass. Differential space use may be due to the species' habitat preferences or swimming abilities. Our findings provide information to inform potential design of mitigation structures, and they also identify the need for additional work required to more fully understand the mechanisms of passage success versus failure for these and other native potamodromous species.